Git for Product Line Engineering

Hello,
I was wondering if anyone of you has applied git to manage the evolution of a
product line. In such a context management of software reuse and permanent
variation becomes necessary.

I think that the distributed character of git as well the easier handling of
branches could be very beneficial in such a context.

Yet I was wondering how the relations between reusable and reused things could
be managed?

If for example I am the maintainer of a library in a product line context I want
to know who pulls from me and whether my library had to undergo any
product-specific changes in any of the other repositories that belong to my
product line.

Regards,
Michalis